The present invention relates to detergent compositions, and in particular, hand laundry compositions containing methylester sulfonate surfactants. In one preferred embodiment, the present invention relates to laundry bar compositions which possess excellent cleaning, whitening/anti-redeposition, foaming properties, and are mild to the skin.
Detergent compositions are well recognized in the art and can vary greatly in composition depending on end use. However, such compositions typically include anionic sulfate or sulfonate surfactants, and in particular linear alkyl benzene sulfonates (LAS).
Hand laundry detergent compositions, such as laundry soap bars, are used for hand laundering clothes at ambient temperatures. It has been found that soap employed for laundry purposes should be a little stronger than that soap used for cosmetic and/or hand use in order to effectively remove soils from fabrics. Moreover, hand laundering compositions are required to have a relatively high degree of foaming. This is in contrast to machine wash compositions where little or no foam is desired.
Hand laundering compositions are also very cost sensitive. In view of the fact that they are typically employed in emerging world economies, cost becomes a significant consideration in formulating these detergent compositions. Most producers of such compositions typically include soap at a 60% level since it is a relatively low cost surfactant. Thus, hand laundering compositions need to provide a suitable combination of performance, foam and cost.
The art has also looked to the improvement of these compositions through the inclusion of additional surfactants such as alkylbenzone sulfonates and in particular, LAS. In making improvements in laundry soap formulations, e.g., through the use of LAS or other alkyl benzene sulfonates, the surfactants are chosen for both their performance and their cost.
In this regard, methyl ester sulfonates have been employed in certain detergent compositions. However, methyl ester sulfonates have normally been employed only in combination with another primary surfactant such as LAS, e.g. in detergent granules and certain liquid detergent products. They have not been found in hand laundry compositions.
Perhaps most significantly, MES as the sole surfactant has failed to meet the cost-foam-performance requirements in soft water environments, and from the performance side, compositions containing both LAS & MES have not provided significant improvements in soft water environments. Thus, MES certainly has not been viewed as a replacement for LAS.
Since one typically expects harder water will lead to poorer foaming and performance, particularly with low cost laundry soap bars, the art has not contemplated the use of MES in detergent compositions for such environments.
In other words, while MES has been employed as an additive in combination with, e.g., LAS, it has not found use as a replacement for LAS. In fact, its relatively poor performance in combination with LAS, has led the art in other directions.